1. Field of the Invention
This invention relates to a method of preparation and compositions prepared thereby. More specifically, this invention is directed to a process which is directive for the synthesis of highly effective UV stabilizer compounds and the products of such process.
2. Description of the Prior Art
The reductive alkylation of amines is well known and can be readily achieved by reaction of an amine and an aliphatic aldehyde, or an aliphatic ketone, in the presence of hydrogen and an appropriate catalyst. Ordinarily, the pressure and temperature conditions prevailing during such reaction must also be carefully selected in order to drive the reaction in the direction of the desired product. Where a diamine is subjected to reductive alkylation under normal conditions, a mixture of products is usually obtained. This mixture will contain compounds having varying degrees of alkylation, (i.e. diamines in which the degrees of alkylation is incomplete and reaction by-products comprising hydroxyl functional compounds corresponding to the carbonyl functional reactant).
The products of the reductive alkylation of diamines are difficult to separate from one another and, therefore, this procedure generally is regarded as inefficient for the preparation of the N,N' alkylated compound. The alkylation of amine functional compounds with a cyclic ketone, when attempted under ordinary processing conditions, also yields similar product mixtures.
But for the difficulty in obtaining acceptable yields and separation of the products obtained by such synthesis, the reductive alkylation of diamine would provide a convenient method for the synthesis of multifunctional stabilizer compounds. For example, it is known that certain keto-functional hindered amines are highly effective UV stabilizers (see U.S. Pat. Nos. 4,190,571 and 4,207,228). These compounds can also reportedly be appended from a polymer backbone and the resultant polymer also be suitable as UV stabilizer.
In comparing the relative advantages of nonpolymeric versus the polymeric stabilizers, it would appear, from the technical literature, that the polymeric stabilizers are more resistant to extraction and diffusion within the polymeric materials, whereas, the non-polymeric systems provide a greater degree of uniformity protection, at comparable concentrations, than the corresponding polymeric system. It would thus appear that each of the foregoing types of stabilizers do suffer from some inherent disadvantage and that an intermediate species of compound would be preferable; namely, one having the resistance to extraction of a polymeric stabilizer and yet the ease of uniformity of distribution within the polymer of a non-polymeric stabilizer.
But for the problems inherent in the reductive alkylation from diamines, the aforementioned keto-functional hindered amines would serve as an attractive alkylating agent and the resultant product could fill this intermediate role. Thus, there is a continuing need for an effective method to synthesize stabilizer compounds so as to render them immobile within a plastic film or fiber and yet provide acceptable protection at low stabilizer concentrations in order to minimize the effect of such stabilizers on the physical properties and processing characteristics of the stabilized plastic.